Among biodegradable resins, polylactic acid resins are now expected to expand applications, because a production cost of L-lactic acid has been reduced by a high-volume production thereof by fermentation of sugars derived from corn and potato, these raw materials are natural agricultural crops and emit a very small amount of total carbon oxides, and the produced resins have high rigidity and good transparency. Polylactic acid resins however have relatively low impact resistance while having high rigidity to make them brittle materials, and thus are very difficult to be used alone in the field that requires impact resistance.
To solve the problem, JP-A-2006-63111 and JP-A-2006-77126 disclose polylactic acid resin compositions having improved impact resistance by cross-linking polylactic acid resins with a cross-linking agent such as a carbodiimide compound.